One Crisis Averted

The crisis with my angelfish seems to have been successfully averted. This video was taken about an hour after the water change and additives:

Notice they no longer appear to be gasping like they had in the earlier video.

I've kept their tank top open to allow more air circulation. Angels do not have a tendency to jump and fortunately the tetras and corydoras in the tank don't, either. I'm continuing to monitor their progress but so far all seems fine.